Analyzers for the testing of liquid analytes are known having automatically and semi-automatically operating devices for removing and inserting stoppers of containers filled with liquids or samples.
From JP-AP 62 006 171 a device is known for removing and inserting a stopper from and into the opening of a container for body fluids arranged in a tray, wherein a tongue-shaped gripper performing lifting and rotating movements frictionally engages the stopper by means of two pivotable clamping jaws. The container is lifted from the tray by means of a clamping/lifting device and positioned and fixed beneath the gripper. Such a device is disadvantageous in that the pivoting movement of the jaws requires movement over a substantial distance, in a manner that can misalign the jaws. A better construction would be one in which the jaws are caused to translate or reciprocate only, as this movement is less likely to jar the containers.
From EP-AP 0 264 456 a device is known in which the stopper is withdrawn from the opening of the container. The device comprises two clamping jaws with needles and supports arranged on both sides of the container as well as an ejector for the stopper operating under spring force. Furthermore, a clamping/lifting device is provided for the container.
For removing the stopper, the container together with the stopper is urged in the direction of its longitudinal axis, that is to say vertically upwards against the ejector and then the clamping jaws are moved radially towards the stopper. In this way, the needles penetrate the stopper. Subsequently, the container is pulled downwards and withdrawn from the stopper by means of the clamping/lifting device. The stopper is removed by the ejector when the clamping jaws have returned to their home position.
Moreover, from the DE-OS 31 41 780 and US-PS 4,217,798 devices are known in which the stoppers are removed by means of a stripper which is arranged laterally with respect to the container and movable normal to its longitudinal axis, thereby pressing against the side of the stopper and then stripping the stopper off the container by tilting it.
It is desired to provide a device of the generic type by means of which stoppers made of different material and having different diameters can easily, reliably and jar-free be removed from and replaced into the opening of a container arranged in a tray. Moreover, the processing rate for the samples is to be increased considerably in order to meet the requirements of a quick and reliable diagnosis.